Nordic Pure 10 x 20 x 1/2 MERV 12 rated flat panel AC air filters consist of an internal frame bonded between flat layers of two different types of electrostatically charged filter media. The first layer is a polyester filter media which acts as a pre-filter, capturing larger airborne particulates. The second layer is a MERV rated smooth poly blend filter material which attracts and captures smaller particulates. MERV 12 1/2” filters will attract and capture dust, pollen, smog, and droplets from sneezes and coughs. 1/2" filters are great for apartments, window units, campers, RVs, and any air system that requires half inch air filters.